The present invention relates to a manufacturing method for a semiconductor device, for example, having a copper wiring and a low-dielectric constant interlayer insulation film.
In recent years, a copper wiring has been used with miniaturization and high-speed operation of a semi conductor device. Further, in order to reduce a wiring interval and to inhibit a delay of an electrical circuit signal due to multiple layering, an interlayer insulation film with a low dielectric constant has been used. As the interlayer insulation film having a low dielectric constant, for example, SiCOH film including CH3 or H bonded to a SiO2 framework has been used.
In such a semiconductor device of a multiple-layered structure using a copper wiring and an interlayer insulation film with a low dielectric constant, a diffusion prevention film having high barrier properties is formed on an interface between a lower-layer copper wiring and the interlayer insulation film in order to prevent copper contained in a lower-layer copper wiring from being diffused into the interlayer insulation film. Such a diffusion prevention film is exposed at a via hole pattern bottom portion when a via hole pattern is formed on the interlayer insulation film. After formation of a wiring groove, the exposed portion of the diffusion prevention film is removed by etching. In this case, a film including Si such as SiN, SiCN or SiC is used as the diffusion prevention film and therefore dry etching using fluorine-based etching gas is commonly performed.
Such etching causes a copper wiring to be exposed at a via hole bottom portion and to be left in the atmosphere in this state until the next process. However, in this state, the copper wiring is corroded as described in Japanese Patent Application Laid-Open No. 2004-356474 (paragraph [0010], etc.).
More specifically, for example, it can be described as follows: Due to dry etching using fluorine-based etching gas, fluorine remains on the exposed copper wiring surface. The remaining fluorine reacts with moisture in the atmosphere and is converted to Cu—F. F reacts with oxygen or an OH group in moisture and converted into Cu oxide or Cu hydroxide. Corrosion of a copper wiring caused in this way poses a problem that it is difficult to obtain desired electrical characteristics.
Fluorine also remains on a via hole inner wall. Fluorine can become an etchant of an interlayer insulation film composed of, especially an inorganic insulation film with a low dielectric constant including CH3 or H bonded to a SiO2 framework. Accordingly, the interlayer insulation film is etched, so that an etching damage layer is formed. In particular, an interlayer insulation film which is porous due to lower dielectric constant of the interlayer insulation film is more vulnerable to damage. The etching damage layer poses a problem that the damage layer absorbs moisture and causes an increase in a dielectric constant when left in the atmosphere.
To suppress an adverse effect of moisture in the atmosphere and fluctuations in characteristics due to the effect as much as possible, an exposure time to the atmosphere after processing by dry etching using fluorine-based etching gas until the next process such as wet etching is strictly controlled. However, it can be hardly said that only controlling the exposure time to the atmosphere is sufficient since, in a case where production suspension occurs due to troubles such as power failure in a production line, only the control method is not sufficient to take proper measures.